Achatina vassei
Encyclopedia
Achatina vassei is a species
of air-breathing land snail
, a terrestrial
pulmonate gastropod mollusk in the family Achatinidae
, the giant African snails.
Of ‘Achatina’ vassei only the holotype
was known up to 2010. The collector of the type shell, Guillaume Vasse, was a French big game hunter, who spent roughly two years (1904-1907) in central Mozambique with his wife, collecting mammals, birds, insects, molluscs (very few), and plants for the Paris Museum of Natural History. The type specimen is stored in the Muséum national d'histoire naturelle
, Paris (MNHN Mollusca No. 21490).
Another discovery of shells at a second locality was published in 2010. Those shells are stored in the Netherlands Centre for Biodiversity Naturalis, Leiden. There appears to be no other museum or collection that holds material of this species.
The systematic position of this species is still unclear because of the lack of anatomical data; this taxon is probably a species with a restricted range centered on the plateau of Central Mozambique.
The type locality is "environs d’Andrada", Andrada
(18°52’S 32°53’E), Mozambique. It is situated just east of the border with Zimbabwe
northeast of Mutare
.
Another shell has been collected from Gorongosa National Park
, Sofala Province
in Mozambique
and published in 2010.
is small compared to what is known from the other achatinids in southern Africa, its length/height is less than 45 mm with about 7½ whorls
. (This description is in contradiction to Connolly (1925), who probably attributes a wrongly identified shell 63.2 mm long to this taxon – a statement not repeated in his 1939 monograph.) The length is always more than two times the maximum diameter, which is situated at about the level of the apex
of the aperture
. The length of the aperture is always less than half that of the shell; the length of the last whorl in front view is always under three quarters of the total length. The apex is comparatively blunt. The whorls are hardly convex, including the body whorl. The aperture is fairly narrow (greatest width just under the middle) with a thin outer lip; the columella is white, short and narrow, concave with a slight twist, obliquely truncate close to the base. The nepionic whorls are wrinkled and granulose, though always worn in the material studied. The sculpture
consists of regular and close wrinkles resulting in a reticulate-granulate pattern, very prominent below the sutures but well visible on all whorls; in addition there are very faint growth striae. All specimens exhibit a close and fine zebra pattern with irregular, orange-brown flames on a yellowish-brown background; there is a very thin and deciduous periostracum
. On the whole this seems to be a well-defined taxon because of the size, shape and sculpture of the shell.
are still feasible. However, the latter can only be done after destroying the shell which for a holotype of a presumably rare species is certainly not advisable. At the moment no suggestion as to generic classification of ‘Achatina’ vassei can be made.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of air-breathing land snail
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
, a terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
pulmonate gastropod mollusk in the family Achatinidae
Achatinidae
Achatinidae is a family of medium to large sized tropical land snails, terrestrial pulmonate gastropod mollusks from Africa...
, the giant African snails.
Of ‘Achatina’ vassei only the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
was known up to 2010. The collector of the type shell, Guillaume Vasse, was a French big game hunter, who spent roughly two years (1904-1907) in central Mozambique with his wife, collecting mammals, birds, insects, molluscs (very few), and plants for the Paris Museum of Natural History. The type specimen is stored in the Muséum national d'histoire naturelle
Muséum national d'histoire naturelle
The Muséum national d'Histoire naturelle is the National Museum of Natural History in Paris, France.- History :The museum was formally founded on 10 June 1793, during the French Revolution...
, Paris (MNHN Mollusca No. 21490).
Another discovery of shells at a second locality was published in 2010. Those shells are stored in the Netherlands Centre for Biodiversity Naturalis, Leiden. There appears to be no other museum or collection that holds material of this species.
The systematic position of this species is still unclear because of the lack of anatomical data; this taxon is probably a species with a restricted range centered on the plateau of Central Mozambique.
Distribution
This species is probably endemic to Central Mozambique. This is an area where little malacological exploration has been carried out.The type locality is "environs d’Andrada", Andrada
Andrada
Andrada may refer to:*Alonso Andrada , a biographer and ascetic writer*Diogo de Paiva de Andrada , Portuguese theologian born at Coimbra...
(18°52’S 32°53’E), Mozambique. It is situated just east of the border with Zimbabwe
Zimbabwe
Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...
northeast of Mutare
Mutare
Mutare is the fourth largest city in Zimbabwe, with a population of around 170,000. It is the capital of Manicaland province.-History:...
.
Another shell has been collected from Gorongosa National Park
Gorongosa National Park
Gorongosa National Park is at the southern end of the Great African Rift Valley in the heart of central Mozambique. The 3,770 square kilometer park includes the valley floor and parts of surrounding plateaus...
, Sofala Province
Sofala Province
Sofala is a province of Mozambique. It has an area of 68,018 km² and a population of 1.676.131 . Beira is the capital of the province. The province is named for the ruined port of Sofala.- Districts :Districts of Sofala Province include:...
in Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
and published in 2010.
Shell description
The somewhat thin and fragile shellGastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
is small compared to what is known from the other achatinids in southern Africa, its length/height is less than 45 mm with about 7½ whorls
Whorl (mollusc)
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...
. (This description is in contradiction to Connolly (1925), who probably attributes a wrongly identified shell 63.2 mm long to this taxon – a statement not repeated in his 1939 monograph.) The length is always more than two times the maximum diameter, which is situated at about the level of the apex
Apex (mollusc)
Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...
of the aperture
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
. The length of the aperture is always less than half that of the shell; the length of the last whorl in front view is always under three quarters of the total length. The apex is comparatively blunt. The whorls are hardly convex, including the body whorl. The aperture is fairly narrow (greatest width just under the middle) with a thin outer lip; the columella is white, short and narrow, concave with a slight twist, obliquely truncate close to the base. The nepionic whorls are wrinkled and granulose, though always worn in the material studied. The sculpture
Sculpture (mollusc)
The sculpture of a mollusc shell is the three-dimensional ornamentation on the outer surface, as distinct from the basic shape of the shell itself or colouration. Sculpture may be concave as well as convex. Sometimes it has microscopic detail. Sculpture refers to the calcareous outer layer, not the...
consists of regular and close wrinkles resulting in a reticulate-granulate pattern, very prominent below the sutures but well visible on all whorls; in addition there are very faint growth striae. All specimens exhibit a close and fine zebra pattern with irregular, orange-brown flames on a yellowish-brown background; there is a very thin and deciduous periostracum
Periostracum
The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...
. On the whole this seems to be a well-defined taxon because of the size, shape and sculpture of the shell.
Anatomy
Unfortunately no material is available for investigating the vital genital anatomy. Incidentally, the animal of the type is still present withdrawn in the shell. This implies that, after more than a century, at least studies of a molecular nature and of the radulaRadula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
are still feasible. However, the latter can only be done after destroying the shell which for a holotype of a presumably rare species is certainly not advisable. At the moment no suggestion as to generic classification of ‘Achatina’ vassei can be made.